1. Field of The Invention
This invention relates to imidated copolymers using indene or polymerizable components of inexpensive naphtha oil and the utilization thereof.
2. Description of Related Art
Many attempts have been made to improve the heat resistance of general-purpose plastics such as acrylonitrile-butadiene-styrene (ABS) resins, high-impact-polystyrene (HIPS) resins, polyvinyl chloride (PVC) resins and the like. In Plastics Vol. 135, No. 9 (1986), it is stated that in order to improve heat resistance of ABS resins and HIPS resins, a styrene-acrylonitrile copolymerization system is subjected to copolymerization wherein part of the styrene is replaced by .alpha.-methylstyrene and p-methylstyrene, so that the heat deformation temperature (HDT) is improved but the effect is not significant.
U.S. Pat. Nos. 4,761,455, 4,681,916, 4,677,164, 4,603,186 and 4,596,856 describe copolymerization of indene with acrylonitrile, .alpha.-methylstyrene, styrene, methyl methacrylate and the like. The resultant copolymers (resins) are improved in heat resistance by the addition of indene. When the copolymers are added to general-purpose plastics, the heat resistance of the blends or compositions is improved. However, the use of indene alone is not satisfactory with respect to the improving effect.
On the other hand, maleic anhydride and maleimide are polymerizable components capable of imparting heat resistance to resins. In Japanese Laid-open Patent Application Nos. 63-90557 and 63-128050 and U.S. Pat. No. 4,408,010, imidated products of styrene-maleic anhydride copolymer (SMA) are used to provide resin compositions by which the heat resistance of general-purpose plastics is improved.
The copolymer of styrene and maleic anhydride has attracted attention as a product capable of imparting heat resistance to general-purpose plastics such as ABS resins, HIPS resins, PVC resin, polystyrene resin and the like. Since the thermal decomposition of styrene-maleic anhydride copolymer (SMA) starts at 200.degree. C., kneading, extrusion molding, injection molding and the like operations wherein general-purpose plastics are used in combination should generally be carried out at temperatures of not lower than 200.degree. C., with an attendant disadvantage that the use of SMA in this field is only under specific conditions.
In order to overcome the disadvantage, partial imidation of SMA has been taken into account. According to U.S. Pat. No. 3,840,499, with copolymers of SMA imidated with ammonia, when an imidation rate increases by 1%, the glass transition temperature raises by about 3.degree. C. In addition, with copolymers of SMA imidated with methylamine, when the imidation rate increases by 1%, the glass transition temperature increases by about 2.degree. C. or more.
In the Polymer Papers (Japan) Vol. 139, p. 447 (1979), the thermal decomposition characteristics of styrene-N-phenylmaleimide copolymer are investigated wherein the starting temperature for thermal decomposition of the styrene-N-phenylmaleimide copolymer is reported as 320.degree. C., which is higher by 120.degree. C. or more than SMA. However, the imidated copolymer obtained only from styrene, maleic anhydride and the maleimide still presents a problem of poor compatibility when used as a heat-resistant resin improver for general-purpose plastics.
Those resins obtained from starting maleic anhydride and/or maleimide have acid anhydride groups and carbonyl groups therein. These functional groups are able to react with amido groups or amino group of polyamide (PA) resins. When utilizing this property, the resins have utility as a compatibilizing agent for PA resins such as nylon and polycarbonate (PC) resins or modified polyphenylene oxide (PPO) resins, which are difficult in fine dispersion only by mechanical means. For this purpose, Japanese Laid-open Patent Application No. 63-90557 and Journal of Japanese Rubber Association Vol. 61, No. 8, P.542 (1988) proposed a partially or wholly imidated product of styrene and maleic anhydride copolymer. The thermal decomposition starting temperature of these products is lower then 320.degree. C. which is the thermal decomposition starting temperature of the styrene and N-phenylmaleimide copolymer which is a wholly imidated copolymer. Even though this imidated copolymer is intended for use as a compatibilizing agent for PA resins and PC resins or modified PPO resins, or as an improver for PA resins, the kneading and molding temperatures are limited to about 300.degree. C., thus the known imidated copolymers presenting the problem for use as a resin improver.
As stated above, many techniques have been proposed for resins or resin compositions (hereinafter referred to as heat-resistant resin improver) capable of imparting heat resistance to general-purpose plastics such as ABS resins, HIPS resins, PVC resin and the like, but have some of the following problems.
(1) The effect as a heat-resistant resin improver is not satisfactory, with the problem with respect to the degrees in improvement of the heat deformation temperature (HDT) and glass transition temperature (Tg) of general-purpose plastics.
(2) When mechanical kneading and extrusion molding or injection molding is determined as being carried out at a temperature of from 200.degree. to 250.degree. C. for compounding and molding general-purpose plastics and heat-resistant resin improvers, there is the problem that the heat decomposition temperature of the known heat-resistant resin improver is in the vicinity of the above temperature range.
(3) When general-purpose plastics and heat-resistant resin improvers are mechanically compounded and molded at given temperatures, the compounding is difficult unless the melt viscosities of both types of resins are close to each other. The melt viscosity of the known heat-resistant resin improver differs form those of general-purpose plastics.
The present invention contemplates to solve the above problems (1) to (3).
Attention has been paid to polyamide resin-based alloyed resins such as polyamide-polycarbonate resin, polyamide-modified polyphenylene oxide resin and the like because of their good mechanical characteristics and chemical resistances.
However, the polyamide-polycarbonate and polyamide-modified polyphenylene oxide resins are not compatible and thus, a compatibilizing agent for finely dispersing the two resins is necessary. Known compatibilizing agents have the following problems.
(4) Known compatibilizing agents have not potential capability of finely dispersing polyamide-polycarbonate and polyamide-modified polyphenylene oxide resins, so the the resultant alloyed resins are unsatisfactory in mechanical characteristics.
(5) The temperature range in which polyamide-polycarbonate resin, polyamide-modified polyphenylene oxide resin or the like is mechanically kneaded and molded is generally in the vicinity of 300.degree. C. In this temperature range, the compatibilizing agent becomes thermally unstable.
The wholly imidated copolymer obtained only from indene and a maleimide is described in Polymer Journal, Vol. 20, No. 11, pp. 979-985 (1988) and Japanese Patent Publication No. 49-26949. However, these publications deal only with a kinetic study and a preparation process using a irradiation polymerization technique and do not suggest the utility as a heat-resistant resin improver or a compatibilizing agent for polyamide resin-based alloys. In addition, the molecular weight of the imidated copolymer is not clarified.
U.S. Pat. No. 4,600,747 describes a flame-resistant ABS resin using a resin composition comprising indene and a maleimide, but the application to the flame-resistant ABS resin is completely different from that of the present invention. In this patent, optimum contents of indene and the maleimide are not stated and it is not known whether or not indene and the maleimide are essential in the composition. In addition, the use of indene and the maleimide is not particularly shown in any example.
The applicants of this invention have already described the copolymer including polymerizable components of naphtha oil as follows.
Naphtha from coal or petroleum has a boiling point of from 80.degree. to 220.degree. C. and is chiefly composed of aromatic hydrocarbons having from 8 to 11 carbon atoms. The naphtha oil contains a component (polymerizable component) having a reactive double bond and composed mainly of indene. Indene has a bicyclic structure which is more rigid than styrene. Accordingly, the resin comprised of a polymerizable indene component can be expected as improving heat resistance. The present inventors made studies on the preparation of copolymers of the polymerizable component in naphtha oil and maleic anhydride and found that copolymers of the polymerizable component in naphtha oil and maleic anhydride could be industrially produced at a higher yield than as reported in Macromol., Chem., 62, 120 (1963) and with different distributions of molecular weight being attained by combination of reaction conditions. The resultant copolymers including alkali hydrolyzates, ester products, alkali hydrolyzates of sulfonated product and non-modified products were found effective as various dispersants, coating compositions, adhesives, heat-resistant resin improvers for general-purpose plastics, compatibilizing agents for polyamide resins and the like and proposed in U.S. patent application No. 372,306 (corresponding to published European Patent Application No. 0348975).
When the copolymers are utilized as an improver for general-purpose plastics, limitation is placed on the compounding conditions with the general-purpose plastics. On the other hand, when they are used as a compatibilizing agent for polyamide resin, the resultant alloyed resins have still a problem on the improvement in mechanical characteristics.